JPH0232152B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a recording sheet written using ink, and in particular, the sheet has high density images and characters recorded on the sheet, clear color tone, fast ink absorption speed, and improved weather resistance. This invention relates to an inkjet recording sheet suitable for multicolor recording. In recent years, inkjet recording methods have been characterized by high speed, low noise, easy multicolor printing, great flexibility in recording patterns, and no need for development or fixing.
It is rapidly becoming popular for a variety of uses, including hard copy devices for various figures including kanji and color images. Furthermore, the images formed by the multicolor inkjet recording method are comparable to those produced by normal multicolor printing, and when the number of copies to be produced is small, the inkjet recording method is preferred over the multicolor printing method because it is cheaper than the normal plate making method. Attempts are being made to apply it to the field of color photography and printing. High-quality paper used for general printing, coated paper, and so-called baryta paper used as a base for photographic paper have extremely poor ink absorption, so when used for inkjet recording, the ink remains on the surface for a long time. If the recording surface is rubbed by touching a part of the device, being touched by the operator, or continuously ejected sheets overlapping,
The image is smeared with residual ink. In addition, if two to four color ink droplets overlap in the same place in high-density image areas or multicolor recording, the amount of ink may be large and the ink may mix without being absorbed or may flow out. It's problematic and impractical. In other words, the recording sheet can produce images with high density and clear tones, and not only absorbs ink quickly and does not run out, but also does not smudge even if touched immediately after printing. ,
At the same time, it is required to suppress the lateral diffusion of ink dots on the surface of the recording sheet and to obtain a high-resolution image without bleeding. Several proposals have been made to solve these problems. For example, JP-A-52-
No. 53012 discloses an inkjet recording paper made by moistening a low-sized base paper with a paint for surface treatment. Also, in JP-A No. 53-49113,
An inkjet recording paper is disclosed in which a sheet containing urea-formalin resin powder is impregnated with a water-soluble polymer. Further, JP-A-55-5830 discloses an inkjet recording paper in which an ink-absorbing coating layer is provided on the surface of the support;
No. 51583 discloses an example in which a non-glue pigment is used as a pigment in the coating layer, and JP-A-55-146786 discloses an inkjet recording paper provided with a water-soluble polymer coating layer. Furthermore, JP-A-55-11829 has a layer structure of two or more layers, the outermost layer has an ink absorbency of 1.5 to 5.5 mm/min, and the second layer has an ink absorbency of 5.5 to 60.0 mm/min. A method for adjusting the spread of ink dots and the absorption speed is disclosed. However, the technical idea as typified by JP-A No. 52-58012 seeks to obtain high image quality by sacrificing ink absorption to some extent, and the technical idea as typified by JP-A-53-49113 Although such technical ideas can achieve a certain level of ink absorption and resolution, they have the disadvantage that the ink penetrates deep into the paper layer, making it difficult to achieve ink density, and both are unsatisfactory as multicolor inkjet recording paper. be. Therefore, as a method to improve these drawbacks, an inkjet recording paper coated with non-cohesive silica powder was disclosed in JP-A-55-51583;
-790 discloses an optically readable barcode printing paper coated with finely powdered silicic acid. By providing a layer of such synthetic silica or other white fine powder on the surface, resolution, color property, color density,
Absorbency, roundness, etc. are greatly improved, but most of the inks used for these recording media are water-soluble inks, and if the image formed on the recording medium gets wet with water, it may cause damage again. It is still unsatisfactory in cases where it is exposed to the outside air, such as in posters, or in photographic applications that are intended to be preserved. Several proposals have been made to solve these problems. For example, JP-A-55-
No. 53591 discloses a recording paper in which a water-soluble salt of a metal is applied to the surface on which recording is performed. Further, JP-A-56-84992 discloses an inkjet recording method in which printing is performed on a recording medium containing a polycationic polymer electrolyte on the surface using an aqueous ink containing a water-soluble direct dye or an acidic dye.
Further, Japanese Patent Application Laid-open No. 55-150396 describes a method for making inkjet recording water resistant by applying a water-resistance agent that forms a lake with the dye in the aqueous ink after inkjet recording using a water-based ink. After inkjet recording with water-based ink on an inkjet recording sheet coated with water-soluble polymer,
A method for making an inkjet recording sheet waterproof by applying a waterproofing agent that makes the water-soluble polymer insolubilized has been disclosed. However, in the methods of using various cationic resins to make images made with water-based inks waterproof, dye mordants such as dicyandiamide condensates, polyamines, and polyethyleneimines have been used.
If these mordants are used in an amount that satisfies water resistance, the white paper may yellow in the air or when exposed to sunlight, and even if the white paper does not yellow, it may reduce the sunlight fastness of the dye in the recorded image. As it turned out, it was difficult to achieve both water resistance and weather resistance (yellowing and light resistance). In order to obtain an inkjet recording paper with improved water resistance and sunlight fastness of water-based ink images, the inventors of the present invention have conducted extensive research on water resistance agents, and have found that they can simultaneously improve water resistance and sunlight fastness. They succeeded in this and came up with the present invention. That is, the present inventors have proposed an inkjet recording method in which a recorded image is obtained by jetting a water-based inkjet onto an image-receiving sheet, in which the image-receiving sheet has a structural formula represented by () in the following general formula as a structural unit. It has been discovered that by containing a basic oligomer at least on the surface, it is possible to form a multicolor recorded image with excellent water resistance and sunlight fastness of water-soluble dyes. In the formula, R ₁ , R ₂ , R ₃ are alkyl groups, m is 1 to 7,
n represents 2 to 10, and Y represents an acid group. Examples of the basic oligomer include Nalpoly 607 (manufactured by Nalco Chemical Co., Ltd.), Polyfix 601 (manufactured by Showa Kobunshi Co., Ltd.), and the like. When inkjet recording is performed on an inkjet recording sheet containing a resin represented by the above general formula () with an aqueous ink containing a direct dye or an acidic dye having an anionic dissociative group, the dye in the aqueous ink and the recording sheet are mixed. The cationic resin binds and prevents dye elution. The content of the cationic resin represented by the general formula () is usually 0.1 to 4 g/m ² , preferably 0.2 to 2
g/m ² can improve the water resistance and weather resistance according to the invention. To apply these materials to recording media, they are made into an aqueous solution, mixed with commonly used binders such as oxidized starch, polyvinyl alcohol, CMC, and other water-soluble cellulose derivatives, etc., and then processed using a size press or roll. Coated paper is coated with a coater or other type of coater, or is coated with a pigment that has high ink absorption ability, such as synthetic silica, synthetic alumina, calcium carbonate, etc., and a binder is added to form a coating layer. At least a cationic resin can be added to the surface by applying the aqueous solution using an air knife coater, roll coater, blade coater, spray, etc., or directly adding it to the coating liquid consisting of the pigment and adhesive to form a coating layer. It is possible to make it a recording medium. On the other hand, the aqueous ink used in the present invention contains at least one of a water-soluble acid dye and a water-soluble direct dye as a dye, and also contains a wetting agent,
Contains dye solubilizers, preservatives, anti-bacterial agents, etc. Examples of water-soluble direct dyes include CI Direct Black, CI Direct Yellow, CI Direct Blue, and CI Direct Red. Examples of water-soluble acid dyes include CI Acid Black, CI Acid Yellow, CI Acid Blue, CI Acid Red, and CI Acid Black. etc. are used, but of course the invention is not limited to these. Such dyes contain -SO ₃ Na-, - in the dye molecule.
The ink has water solubility due to SO ₃ H and -NH ₂ groups, but when such an ink is attached to and absorbed on the surface of the recording medium, the anionic groups of the dye in the ink and the The cationic fluorescent agent contained in the recording material forms an ionic bond to form a water-insoluble salt, which improves the water resistance of the image and does not reduce its fastness to sunlight. The present invention will be described below with reference to examples, but it is not limited to these examples. In addition, parts and percentages shown in the examples mean parts by weight and percentages by weight. Methods for measuring various physical property values in Examples are shown below. (1) Water resistance Cyan (C), Magenta (M), Yellow (Y),
The image obtained by solid printing with each Black (Bl) ink was air-dried for 1 hour, then immersed in water at 30℃ for 3 minutes, and the image density before and after immersion was measured using a Macbeth densitometer RD514. The percentage obtained by dividing by the concentration before immersion was used as a measure of water resistance. The higher the value, the better the water resistance. (2) Light resistance Images obtained by solid printing with C, M, Y, and Bl inks were heated at 40°C using a xenon fade meter (FAL-25X-HCL model manufactured by Suga Test Instruments Co., Ltd.).
Irradiate for 40 hours at 60% illuminance and 63W/ ^m2 , and measure the color density before and after irradiation using a Macbeth densitometer RD514.
The light resistance was measured as a percentage of the concentration after irradiation divided by the concentration before irradiation. The higher the value, the better the light resistance. (3) White paper yellowing The recording paper was left in a room at 20°C and 65% RH for one month, and the degree of yellowing on the recording surface was visually determined. X...
Obvious discoloration, △...slight discoloration, 〇...almost no discoloration. Example 1 80 parts of LBKP with a water content of 350ml, a water content of 400ml
To a pulp slurry consisting of 20 parts of NBKP, 25 parts of calcium carbonate PC (light calcium carbonate manufactured by Shiroishi Kogyo Co., Ltd.) was added as a filler, and 1 part of CatoF (cationized starch manufactured by Oji Nacional Co., Ltd.) was added as a retention improver and paper strength improver. A base paper with a basis weight of 60 g/ ^m2 is made using a Fourdrinier paper machine, and a size press machine is used to make paper using MS3800.
A size press solution consisting of 4% oxidized starch (manufactured by Nippon Shokuhin Co., Ltd.) and 1% oligomer (Nalpoly 607 manufactured by Nalco Chemical Co., Ltd.) represented by the following structural formula () was deposited at a solid content of 3.2 g/m ² and dried. The sheet was used as the recording paper of Example 1. For comparison, a product was produced in exactly the same manner as in Example 1, except that the oligomer in Example 1 was replaced with polyethyleneimine (Epomin P1000, manufactured by Nippon Shokubai Kagaku Co., Ltd.) and dicyandiamide formalin condensate (Sunfix 70, manufactured by Sanyo Chemical Co., Ltd.). The sheets were used as recording sheets of Comparative Example 1 and Comparative Example 2, respectively, and the water resistance, light resistance, and white paper yellowing of these papers were measured. The results are shown in Table 1. where n is an oligomer of 2 to 10

[Table] It is clear from Table 1 that Example 1 is superior to the comparison in terms of white paper yellowing, water resistance, and light resistance. Example 2 90 parts of LBKP with a water content of 380 ml, a water content of 410 ml
10 parts of talc as a filler was added to a pulp slurry consisting of 10 parts of NBKP, 0.3 parts of a rosin sizing agent,
80 parts of synthetic silica and 20 parts of heavy calcium carbonate were added as pigments to coated base paper, which was made by adding 2.2 parts of Bando and making paper using a fourdrinier paper machine, and applying 2.8 g/ ^m2 of oxidized starch as a solid content using a size press machine. Add 13 parts of polyvinyl alcohol as an adhesive to the thriller, and apply a paint containing antifoaming agents, flow modifiers, preservatives, hardeners, etc. as appropriate using an air knife coater to a solid content of 16 g/ ^m2. , was used as the base paper. A coating solution consisting of 3% polyvinyl alcohol and 3% of the same oligomer as used in Example 1 was prepared, coated on the surface of the base paper using an air knife coater, and dried to a solid content of 2 g/m ² . Next, it was lightly supercalendered and Example 2 was prepared.
It was used as a recording paper. For comparison, liquid was used instead of oligomer as a resin used in combination with the above polyvinyl alcohol.
LC-3 (styrene-maleic acid monoalkyl ester-cation copolymer manufactured by Kindai Kagaku Kogyo Co., Ltd.), Nikawaroku D1000 (manufactured by Nippon Carbide Co., Ltd., dicyandiamide condensate), Wistex-T101 (manufactured by Nagase Sangyo Co., Ltd.) ) Comparative Examples 3, 4, and 5 were prepared in exactly the same manner as in Example 2, except that the following materials were used. Table 2 shows the results of measuring the water resistance and weather resistance of these recording papers.

[Table] From Table 2, Comparative Example 3 has insufficient water resistance, and Comparative Examples 4 and 5 have poor light resistance.
It is clear that both water resistance and light resistance are improved. Example 3 Oligomer used in Example 2 (Nalpoly
Example 2 was repeated except that Polyfix 601 (manufactured by Showa Kobunshi Co., Ltd., n is about 8 to 10) was used instead of Polyfix 607). The recording paper obtained in Example 3 had almost the same water resistance and light resistance as the recording paper of Example 2, and was superior.

Claims (1)

[Scope of Claims] 1. An inkjet recording method for recording on a recording medium containing at least a cationic resin on its surface using an aqueous ink containing a water-soluble direct dye and/or a water-soluble acid dye. An inkjet recording paper, wherein the cationic resin is a basic oligomer having a structural unit represented by the following general formula (). In the formula, R ₁ , R ₂ , R ₃ are alkyl groups, m is 1 to 7,
n represents 2 to 10, and Y represents an acid group.